Cellular communication systems ring called parties by sending ring-alert messages on a cell's broadcast channels. Ring-alert messages are directed to particular subscriber units. The subscriber units monitor the broadcast channels to determine when a ring-alert message is directed to a particular subscriber unit.
In cellular systems, ring-alerts are generally broadcasted in all cells of an entire geographic region where the called-party may reside. Broadcasting each ring-alert within a particular cell requires a certain amount of additional energy. In terrestrial cellular systems, there is no need to conserve energy because the energy supply is virtually unlimited. However, in a satellite communication system, where subscriber units receive ring-alerts from satellite communication nodes, it is desirable to conserve energy by broadcasting ring-alerts in as few antenna beams as possible, since a satellite's energy supply is extremely limited. For example, a satellite's power is generally limited to that supplied by its solar panels, and its batteries. Energy expended for ring-alerts reduces the amount of energy available for other communications.
Thus, what is needed are a method and apparatus to conserve energy onboard a satellite communication station that issues ring-alerts and pages. Moreover, what is needed are a method and apparatus for reducing the amount of power expended in transmitting ring-alerts in satellite-based communication systems. What is also needed are a method and apparatus for broadcasting ring-alerts and pages in as few antenna beams as possible in satellite communication systems.